To demonstrate the potential for geol. Fluid samples were obtained before CO2 injection for baseline geochem. Following CO2 breakthrough at the observation well, brine samples showed sharp drops in pH, pronounced increases in HCO3- and aq. Fe, and significant shifts in the isotopic compns. Based on a calibrated 1-D radial flow model, reactive transport modeling was performed for the Frio-I Brine Pilot.
A simple kinetic model of Fe release from the solid to aq. Fe concn. Brine samples collected after half a year had lower Fe concns. The paper provides a method for estg. Long-term simulations show that the CO2 plume gradually spreads outward due to capillary forces, and the gas satn. The gas phase is predicted to disappear after years. Elevated aq. CO2 concns.
Biotite—brine interactions under acidic hydrothermal conditions: Fibrous illite, goethite, and kaolinite formation and biotite surface cracking Environ. American Chemical Society. To ensure safe, efficient geol. After h reaction, fast growth of fibrous illite on biotitite flat basal planes was obsd. After h reaction, the biotite basal surface cracked, resulting in illite detaching from the surface.
Later on after h , the cracked surface layer was released into soln. Cracking and detachment of the biotite surface layer increased the surface area in contact with soln. On biotite edge surfaces, Al-substituted goethite and kaolinite pptd.
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In control expts. Results provided unique information on biotite-brine interaction under acidic hydrothermal conditions. Dissolution and precipitation of clay minerals under geologic CO 2 sequestration conditions: CO 2 —brine—phlogopite interactions Environ. To ensure efficiency and sustainability of geol. CO2 sequestration GCS , a better understanding of geochem. This work examd. Phlogopite served as a clay mineral model for potential GCS sites. During the reaction, phlogopite dissoln. Although the bulk soln. Nano-particles first appeared on the edges of dissoln.
Amorphous SiO2 and kaolinite were identified as the secondary mineral phases; qual. Results provided new information on the evolution of morphol. Effects of salinity and the extent of water on supercritical CO 2 -induced phlogopite dissolution and secondary mineral formation Environ. To ensure the viability of geol.
CO2 sequestration GCS , a holistic understanding of reactions at super-crit. Salinity enhanced phlogopite dissoln. In low salinity solns.
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The effects of initial acetate on scCO 2 -brine-anorthite interactions under geologic CO 2 sequestration conditions Energy Environ. Acetate is one of the most abundant org. CO2 sequestration GCS. This work studied the effect of initially present acetate on the dissoln. Anorthite was chosen as a model mineral because of the abundance of feldspar in clayey sandstones and the possibility of metal carbonation.
In this study, acetate was found to decrease the cumulative aq. The extent of the effect of acetate on metal concn. For anorthite dissoln. For secondary mineral pptn. The presence of kaolinite as a secondary mineral was confirmed using high resoln. An increase in the relative amt.
These results provide new insights for understanding and predicting GCS system evolution upon scCO2 injection in the initial presence of acetate. Elsevier Ltd. A review. Before implementing CO2 storage on a large scale its viability regarding injectivity, containment and long-term safety for both humans and environment is crucial. Assessing CO2-rock interactions is an important part of that as these potentially affect phys.
Increased understanding of the phys. Several areas of interactions can be defined: 1 interactions during the injection phase and in the near well environment, 2 long-term reservoir and cap rock interactions, 3 CO2-rock interactions along leakage pathways well, cap rock and fault , 4 CO2-rock interactions causing potable aquifer contamination as a consequence of leakage, 5 water-rock interactions caused by aquifer contamination through the CO2 induced displacement of brines and finally engineered CO2-rock interactions 6.
The driving processes of CO2-rock interactions are discussed as well as their potential impact in terms of changing phys. This includes dissoln. Then the methodologies for assessing CO2-rock interactions are discussed. High priority research topics include the impact of other gaseous compds. To investigate the potential for the geol. As injected CO2 gas reached the observation well, results showed sharp drops in pH 6. Post-injection results show the brine gradually returning to its pre-injection compn. Monitoring of fluid—rock interaction and CO 2 storage through produced fluid sampling at the Weyburn CO 2 -injection enhanced oil recovery site, Saskatchewan, Canada Appl.
Emberley, S. The Weyburn oilfield is a carbonate reservoir in south central Saskatchewan, Canada and is the site of a large CO2 injection project for purposes of enhanced oil recovery. The Weyburn field, in the Mississippian Midale Formation, was discovered in and was under primary prodn.
The reservoir comprises two units, the Vuggy and the Marly, and primary and secondary recovery are thought to only have significantly depleted the Vuggy zone, leaving the Marly with higher oil saturations. In Pan Canadian Resources now EnCana , the operator of the field, began tertiary recovery by injection of CO2 and water, primarily into the Marly strata. The advent of this project was an opportunity to study the potential for geol. Using 43 Baseline samples collected in August , before CO2 injection at Weyburn, and 44 monitoring samples collected in Mar. By the time of Baseline sampling the produced water had been dild.
Based on chem. After 6 mo of injection of CO2, the general patterns are changed very little, except that the pH has decreased by 0. Field measured pH had increased and alky. Some initial modeling of water-rock reactions suggests that silica sources are available to the water resident in the Midale formation, and that clay minerals may well be capable of acting as pH buffers, allowing injected CO2 to be stored as carbonate minerals. Further work is underway to document the mineralogy of the Midale formation and assocd. In this paper we present the results of an integrated field and exptl.
Prior to the CO2 injection, we collected formation water and rock samples from the reservoir, and conducted lab. About 1 yr after stopping the CO2 injection, we again collected formation fluid using a Cased Hole Dynamics Tester CHDT at one of the three observation wells where CO2 breakthrough was confirmed by time-lapse well logging. The field results were quite similar to the lab.
Our results demonstrated the potential of CO2 storage by formation water dissoln. A Chem. Lu, Jiemin; Kharaka, Yousif K. A highly integrated geochem. The program included extensive field geochem. Results show that mineral reactions in the Lower Tuscaloosa reservoir were minor during CO2 injection.
Brine chem. Field fluid sampling and lab. Carbon-isotopic compn. The reservoir rock, which is composed mainly of minerals with low reactivity av. The significance of low reactivity is both pos. An improved model calculating CO 2 solubility in pure water and aqueous NaCl solutions from to K and from 0 to bar Chem. Elsevier Science B. A thermodn. NaCl solns. The model is based on a specific particle interaction theory for the liq.
With this specific interaction approach, this model is able to predict CO2 soly. Comparison of the model predictions with exptl. Sedimentary basins. In Treatise on Geochemistry ; Pergamon : Oxford , ; pp 1 — Springer : New York , ; pp — Injection of CO 2 -saturated water through a siliceous sandstone plug from the Hontomin test site N Spain. Experiment and modeling Environ. Dewetting of silica surfaces upon reactions with supercritical CO 2 and brine: Pore-Scale studies in micromodels Environ.
Wettability of reservoir minerals and rocks is a crit. Very little information on wettability in supercrit. CO2 scCO2 -mineral-brine systems is available. The authors studied pore-scale wettability and wettability alteration in scCO2-silica-brine systems using engineered micromodels transparent pore networks , at 8. Dewetting of silica surfaces upon reactions with scCO2 was obsd. Given the abundance of silica surfaces in reservoirs and caprocks, these results indicate that CO2 induced dewetting may have important consequences on CO2 sequestration including reducing capillary entry pressure, and altering quantities of CO2 residual trapping, relative permeability, and caprock integrity.
Fundamental studies of crude oil-surface water interactions and its relationship to reservoir wettability J. A fundamental understanding of the wettability of rock surfaces by crude oil and brine requires a good description of the intermol. The aim of our study was to directly measure those interactions and to establish their implications for obsd.
A Surface Forces App. SFA was used to measure the adsorption on and the forces between two molecularly smooth mica surfaces confining thin films of crude oil, brine or both, at different conditions of pH and salinity. By modifying one or both surfaces by controlled pre-adsorption of surface-active polar species from the crude oil, the interaction between mica and oil in brine, or oil and oil in brine was also detd. From contact angle measurements a wettability map' was established for the system investigated showing the regions of different contact angles or wettability' as a function of pH and ionic strength.
This wettability map was found to be correlated with the independently measured surface forces and adsorption. The relative importance of different colloidal forces van der Waals, electrostatic, etc. It is shown that in addn. It was further established that the concept of an intrinsically oil-wet or water-wet surface or reservoir cannot, in general, be correct: depending on the nature of the oil and brine, different species in a crude oil will adsorb on the mineral surfaces and at the oil-water interface, thereby detg.
Monitoring of the microbial community composition in saline aquifers during CO 2 storage by fluorescence in situ hybridisation Int. This study reveals the first analyses of the compn. Microbial monitoring during CO2 injection has been reported.
By using fluorescence in situ hybridization FISH , we have shown that the microbial community was strongly influenced by the CO2 injection. The microbial community was dominated by the domain Bacteria that represented approx. Both the total cell counts as well as the counts of the specific physiol. Our study revealed temporal outcompetition of sulfate-reducing bacteria by methanogenic archaea.
In addn. Experimental study of crossover from capillary to viscous fingering for supercritical CO 2 -water displacement in a homogeneous pore network Environ. Reactive transport modeling of effects of convective mixing on long-term CO 2 geological storage in deep saline formations Int. The existing form of the injected CO2 gas is very important to the feasibility and security of CO2 storage projects in specific geol. The residual gas, soly. Reactive transport simulations were performed to study the dissoln.
According to the changes in gaseous and aq. CO2, the authors divided the simulation process into four stages: 1 dissoln. Sensitivity modeling indicated brine salinity, initial CO2 gas satn. Liquid CO 2 displacement of water in a dual-permeability pore network micromodel Environ. Permeability contrasts exist in multilayer geol. To improve understanding of heterogeneous pore-scale displacements, liq. CO2 LCO2 -water displacement was evaluated in a pore network micromodel with two distinct permeability zones. LCO2 displaced water only in the high permeability zone at low injection rates with the mechanism shifting from capillary fingering to viscous fingering with increasing flow rate.
At high injection rates, LCO2 displaced water in the low permeability zone with capillary fingering as the dominant mechanism. LCO2 satn. SLCO2 as a function of injection rate was quantified using fluorescent microscopy. In all expts. A continuum-scale two-phase flow model with independently detd. Agreement with the micromodel expts. However, the numerical model does not account for the unstable viscous fingering processes obsd.
Monitoring CO 2 intrusion and associated geochemical transformations in a shallow gorundwater system using complex electric methods Environ. Experimental evaluation of wellbore integrity along the cement-rock boundary Environ. Stauffer, Philip H. CO2 sequestration. Simulations sample from probability distributions for each uncertain parameter, leading to global uncertainty ests. Each underlying process in the system-level model is built as a module which can be modified as the simulation tool evolves toward more complex problems.
This approach is essential in coupling processes governed by different sets of equations operating at different time-scales. The basic formulation of the system level model is explained, then the suite of process-level modules linked to the system level are described, and an in-depth example which describes the system-level coupling between injection and economic modules is given. The example showed how physics-based calcns. Dissolution of a mineral phase in potable aquifers due to CO 2 releases from deep formations; effect of dissolution kinetics Energy Convers.
Injection of supercrit. CO2 into deep saline aquifers is a technique for sequestration of large amts. Because complete characterization of these geol. If the leaking CO2 were to reach shallow groundwater aquifers, it could lead to geochem. Identification and assessment of these effects is necessary to analyze risks assocd. Numerical simulations were conducted for a series of CO2 release scenarios and different aquifer geochem. The effect of CO2 induced pH changes as well as trace metal solubilization was assessed using a geochem. Results show that elevated CO2 levels in freshwater aquifers can enhance the dissoln.
Transport models demonstrate the importance of assessing the areal extent of this CO2 release, as well as the need to gain thorough understanding of the key kinetic processes related to CO2 solubilization and the dissoln. Zheng, Liange; Apps, John A. A field expt. MSU-ZERT field program, food-grade CO2 was injected over a 30 day period into a horizontal perforated pipe a few feet below the water table of a shallow aquifer.
The impact of elevated CO2 concns. Field measurements and lab. The geochem. PCA to 1 understand potential correlations between aq. These evaluations were used to assess possible geochem.
Reasonable agreement between obsd. Review of integrity of existing wells in relation to CO 2 geological storage: What do we know? Carbon dioxide storage in geol. However, in certain cases there are flow pathways, natural or manmade, conducive to CO2 leakage. Depending on their condition, existing oil and gas wells may provide such leakage pathways due to either mech. In the case of CO2 storage, there is a concern that well cement in existing wells will degrade in the presence of water-satd.
In this paper we review the status of knowledge in regard to the failure of existing wells, with special attention to the lab. Extensive carbonation has been obsd. However, in CO2-rich environments, severe cement degrdn. This is not expected under typical geol. Microbially enhanced carbon capture and storage by mineral-trapping and solubility-trapping Environ. Mitchell, Andrew C. The potential of microorganisms for enhancing C capture and storage CCS via mineral-trapping where dissolved CO2 is pptd. The bacterial hydrolysis of urea ureolysis was studied in microcosms including synthetic brine SB mimicking a prospective deep subsurface CCS site with variable headspace pressures [p CO2 ] of 13C-CO2.
This demonstrated that ureolysis was effective at pptg. When one of these is found, it is necessary to move the search away from it if the experimenter is looking solely for local minima and transition structures. This leads to the evaluation of the total energy as a sum of the electronic energy at fixed nuclei positions and the repulsion energy of the nuclei. A notable exception are certain approaches called direct quantum chemistry , which treat electrons and nuclei on a common footing. Density functional methods and semi-empirical methods are variants on the major theme.
For very large systems, the relative total energies can be compared using molecular mechanics. The ways of determining the total energy to predict molecular structures are:. This does not imply that the solution is an exact one; they are all approximate quantum mechanical calculations.
It means that a particular approximation is rigorously defined on first principles quantum theory and then solved within an error margin that is qualitatively known beforehand. The simplest type of ab initio electronic structure calculation is the Hartree—Fock method HF , an extension of molecular orbital theory , in which the correlated electron-electron repulsion is not specifically taken into account; only its average effect is included in the calculation. As the basis set size is increased, the energy and wave function tend towards a limit called the Hartree—Fock limit.
Many types of calculations termed post-Hartree—Fock methods begin with a Hartree—Fock calculation and subsequently correct for electron-electron repulsion, referred to also as electronic correlation. To obtain exact agreement with experiment, it is necessary to include relativistic and spin orbit terms, both of which are far more important for heavy atoms. In all of these approaches, along with choice of method, it is necessary to choose a basis set.
This is a set of functions, usually centered on the different atoms in the molecule, which are used to expand the molecular orbitals with the linear combination of atomic orbitals LCAO molecular orbital method ansatz. Ab initio methods need to define a level of theory the method and a basis set. The Hartree—Fock wave function is a single configuration or determinant. In some cases, particularly for bond breaking processes, this is inadequate, and several configurations must be used. Here, the coefficients of the configurations, and of the basis functions, are optimized together.
The total molecular energy can be evaluated as a function of the molecular geometry ; in other words, the potential energy surface. Such a surface can be used for reaction dynamics. The stationary points of the surface lead to predictions of different isomers and the transition structures for conversion between isomers, but these can be determined without a full knowledge of the complete surface. A particularly important objective, called computational thermochemistry , is to calculate thermochemical quantities such as the enthalpy of formation to chemical accuracy.
To reach that accuracy in an economic way it is necessary to use a series of post-Hartree—Fock methods and combine the results. These methods are called quantum chemistry composite methods. Density functional theory DFT methods are often considered to be ab initio methods for determining the molecular electronic structure, even though many of the most common functionals use parameters derived from empirical data, or from more complex calculations. In DFT, the total energy is expressed in terms of the total one- electron density rather than the wave function.
In this type of calculation, there is an approximate Hamiltonian and an approximate expression for the total electron density. DFT methods can be very accurate for little computational cost. Some methods combine the density functional exchange functional with the Hartree—Fock exchange term and are termed hybrid functional methods.
Semi-empirical quantum chemistry methods are based on the Hartree—Fock method formalism, but make many approximations and obtain some parameters from empirical data. They were very important in computational chemistry from the 60s to the 90s, especially for treating large molecules where the full Hartree—Fock method without the approximations were too costly. The use of empirical parameters appears to allow some inclusion of correlation effects into the methods. Primitive semi-empirical methods were designed even before, where the two-electron part of the Hamiltonian is not explicitly included.
In many cases, large molecular systems can be modeled successfully while avoiding quantum mechanical calculations entirely. Molecular mechanics simulations, for example, use one classical expression for the energy of a compound, for instance the harmonic oscillator. All constants appearing in the equations must be obtained beforehand from experimental data or ab initio calculations. The database of compounds used for parameterization, i.
A force field parameterized against a specific class of molecules, for instance proteins, would be expected to only have any relevance when describing other molecules of the same class. These methods can be applied to proteins and other large biological molecules, and allow studies of the approach and interaction docking of potential drug molecules.
Computational chemical methods can be applied to solid state physics problems. The electronic structure of a crystal is in general described by a band structure , which defines the energies of electron orbitals for each point in the Brillouin zone. Ab initio and semi-empirical calculations yield orbital energies; therefore, they can be applied to band structure calculations. Since it is time-consuming to calculate the energy for a molecule, it is even more time-consuming to calculate them for the entire list of points in the Brillouin zone.
The potential representing the interatomic interaction is given by the potential energy surfaces. In general, the potential energy surfaces are coupled via the vibronic coupling terms.
The most popular methods for propagating the wave packet associated to the molecular geometry are:. Molecular dynamics MD use either quantum mechanics , molecular mechanics or a mixture of both to calculate forces which are then used to solve Newton's laws of motion to examine the time-dependent behaviour of systems.
The result of a molecular dynamics simulation is a trajectory that describes how the position and velocity of particles varies with time. It is useful for simulating very large molecules such as enzymes. The atoms in molecules QTAIM model of Richard Bader was developed to effectively link the quantum mechanical model of a molecule, as an electronic wavefunction, to chemically useful concepts such as atoms in molecules, functional groups, bonding, the theory of Lewis pairs , and the valence bond model.
Bader has demonstrated that these empirically useful chemistry concepts can be related to the topology of the observable charge density distribution, whether measured or calculated from a quantum mechanical wavefunction. Many self-sufficient computational chemistry software packages exist. Some include many methods covering a wide range, while others concentrate on a very specific range or even on one method. Details of most of them can be found in:. From Wikipedia, the free encyclopedia. Main article: Ab initio quantum chemistry methods.
Main article: Density functional theory. Main article: Semi-empirical quantum chemistry methods. Main article: Molecular mechanics. Main article: Computational chemical methods in solid state physics. Main article: Molecular dynamics.
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Molecular Modeling of Geochemical Reactions: An Introduction
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